Salmon in Patagonia Show Diverse Lineage

Jonathan Wright
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December 15, 2017

Chinook salmon at Austral Kings (australkings.com) average 35 pounds, but fish over 50 pounds are caught weekly. More important, there are huge numbers of salmon visibly rolling through much of the prime season and they are chrome-bright and full of fight near tidewater. This photo originally appeared in the April-May 2017 issue of Fly Fisherman in the story "Rise of the Southern Kingdom." Ken Morrish photo

Salmon in Patagonia have become big business, both for aquaculture and sportsmen. Deliberate and accidental introductions of pacific salmon in the binational region that encompasses areas of both Chile and Argentina have established self-sustaining populations of anadromous fish that run from the ocean to headwater streams to spawn. New genomics research published in the online scientific journal Nature.com is showing a wide diversity in the genetic lineage of non-native Chilean salmon that can be traced to various sources.

Initial commercial attempts to stock Chinook salmon (Oncorynchus Tshawytscha) worldwide date back to the 1870's, but outside of their native range in the pacific northwest, only populations in New Zealand and Patagonia have become embedded in local ecologies. Prior to their introduction, neither region had native salmonids, owing to their positions in the southern hemisphere and the thermal isolation tropical seas present to migration for cold water species. And while the strains of fish that have adapted well to the South Island of New Zealand have origins that can be traced to specific gene pools of the Sacramento river in California, the fish of Patagonia show more genetic diversity spread over a much larger geographic area, with wider climate and aquatic variables. The success of various bloodlines in diverse stream and river environments may give an indication of how certain races of fish may have become better adapted to specific conditions in North America that are paralleled in Patagonia.

Researchers Cristian Correa of the Universidad Austral de Chile and Paul Moran from the Northwest Fisheries Science Center in Seattle sampled tissue from fin clips taken from Chinook captured in coastal Chile across a wide area ranging from 39 to 48 degrees south latitude. This represents a distance of nearly 800 miles. With the advent of salmon aquaculture in the late 1970's and early 1980's, many new strains of fish were introduced to the region via both open-ocean and net-pen operations. Open-ocean farming techniques release juvenile fish from hatchery operations into waters that flow to the ocean, where the fish mature and return to the streams to spawn, homing in on them via a poorly understood mechanism that probably includes both olfactory and magnetic geolocation. Net-pen operations, on the other hand, raise fish in enclosed pens in salt water pens offshore for the entire life of the fish, when they are harvested. However, net-pen operations have proven to not have acheived 100% containment of their product, with large numbers of both reported and unreported fish escaping into the environment.

In contrast to the New Zealand fish and the incidence of a very small number of Chinook sampled in the Chilean far South that show Sacramento genetics (below 51 degrees south, where limited farming is conducted), the fish in the northern reaches all appear to have come from Lower Columbia River and Puget Sound stock, with certain rivers seeming to have favored specific races of fish. An example of this would be where three strains of Chinook were introduced into a small stream on Quinchao Island, Chiloe at 42 degrees south. The fish had origins from the Cowlitz river spring run originating from the west slope of the Cascades in Washington, a strain from the Bonneville Hatchery on the Columbia, and a strain from the University of Washington at Seattle of unnamed origin. Of the three, only the Cowlitz spring run became established, raising questions of whether conditions in the Chilean stream were favorable to fish that had attributes for spring run spawning, such as lower temperatures or other chemistry such as elevated tannins from snowmelt.

If adaptive characteristics in specific races of fish that provide advantages in the natural world can be identified, then conservation efforts in reintroduction of native fishes to remediated or newly protected environments could be enhanced. Insights being provided via the new sciences of genomics and metabolomics are beginning to show promise for more effective management of fish living in the wild.

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